This is a study of the mechanisms involved in the activation of lymphocytes by sodium periodate. It addresses itself to the following questions: What is the nature of the 10 to the minus 4th power lymphocyte interaction which triggers transformation? We are specifically attempting to measure the effect of the 10 to the minus 4th power lymphocyte interaction on the lipids, proteins and carbohydrate of the cell surface. What is the sequence of biochemical and morphologic events triggered by 10 to the minus 4th power which ultimately lead to cell division? What are the properties of cells which determine whether they will respond to 10 to the minus 4th power stimulation? Does this involve surface immunoglobulins or other detectable differences in lymphocyte populations? What is the responsiveness of lymphocytes from patients with diseases in which lymphocyte function is impaired and, if they differ from normal, does the detection of those differences have any potential clinical value? We expect that the results obtained from this study should provide important insights into regulatory mechanisms affecting cell proliferation and cell mediated immunity.